The instant invention relates to a method for extracting taxanes from mixtures containing such compounds, and particularly for extracting taxanes from plant or plant-derived materials. The taxanes extracted may be used as pharmaceuticals, or may be used as intermediates in the preparation of pharmacologically active taxanes.
Taxanes are diterpene compounds which find utility in the pharmaceutical field. For example, taxol, a taxane having the structure: 
has been found to be an effective anticancer agent, particularly useful in the treatment of ovarian cancer. Cephalomannine, also a taxane, has been reported as a chemotherapeutic agent for the remission of leukemia in U.S. Pat. No. 4,206,221.
Taxanes such as those above may be found in plant materials, and have been isolated therefrom. For example, the extraction of taxol from trees of the Taxus genus using liquid methanol has been reported. However, taxanes are generally present in plant materials in relatively small amounts so that, in the case of taxol, for example, large numbers of the slow-growing yew trees forming a source for the compound may be destroyed. Further, large amounts of organic solvents may be employed in a conventional liquid extraction, which may be time consuming as well. Thus, the art has continued to search for ever more efficient and environmentally safe methods for obtaining taxanes which minimize the use of plant materials and organic solvents.
The instant invention provides a method for extracting a taxane from a mixture containing such taxane and, particularly, for extracting a taxane from a plant or plant-derived material, comprising the step of contacting the mixture with a supercritical fluid capable of solubilizing at least part of the taxane contained therein.
The instant invention provides an efficient method for obtaining taxanes from mixtures with other compounds or materials, and is especially useful in separating taxol, a potent anticancer agent, from trees of the Taxus genus.